[xen stable-4.18] x86: arrange for ENDBR zapping from <vendor>_ctxt_switch_masking()

[patchbot@xxxxxxx]

commit b6fad02a54da8c38a316eeebab22152f29ee0218
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Mon Feb 5 10:44:46 2024 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Apr 9 16:45:01 2024 +0100

    x86: arrange for ENDBR zapping from <vendor>_ctxt_switch_masking()
    
    While altcall is already used for them, the functions want announcing in
    .init.rodata.cf_clobber, even if the resulting static variables aren't
    otherwise used.
    
    While doing this also move ctxt_switch_masking to .data.ro_after_init.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    (cherry picked from commit 044168fa3a65b6542bda5c21e373742de1bd5980)
---
 xen/arch/x86/cpu/amd.c    | 5 +++++
 xen/arch/x86/cpu/common.c | 2 +-
 xen/arch/x86/cpu/intel.c  | 5 +++++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/cpu/amd.c b/xen/arch/x86/cpu/amd.c
index d43288ae97..808cda46bc 100644
--- a/xen/arch/x86/cpu/amd.c
+++ b/xen/arch/x86/cpu/amd.c
@@ -258,6 +258,11 @@ static void cf_check amd_ctxt_switch_masking(const struct 
vcpu *next)
 #undef LAZY
 }
 
+#ifdef CONFIG_XEN_IBT /* Announce the function to ENDBR clobbering logic. */
+static const typeof(ctxt_switch_masking) __initconst_cf_clobber __used csm =
+    amd_ctxt_switch_masking;
+#endif
+
 /*
  * Mask the features and extended features returned by CPUID.  Parameters are
  * set from the boot line via two methods:
diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index 51509fece0..61e5e52151 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -119,7 +119,7 @@ static const struct cpu_dev default_cpu = {
 static const struct cpu_dev *this_cpu = &default_cpu;
 
 static DEFINE_PER_CPU(uint64_t, msr_misc_features);
-void (* __read_mostly ctxt_switch_masking)(const struct vcpu *next);
+void (* __ro_after_init ctxt_switch_masking)(const struct vcpu *next);
 
 bool __init probe_cpuid_faulting(void)
 {
diff --git a/xen/arch/x86/cpu/intel.c b/xen/arch/x86/cpu/intel.c
index aef8e4506c..19466b89e8 100644
--- a/xen/arch/x86/cpu/intel.c
+++ b/xen/arch/x86/cpu/intel.c
@@ -220,6 +220,11 @@ static void cf_check intel_ctxt_switch_masking(const 
struct vcpu *next)
 #undef LAZY
 }
 
+#ifdef CONFIG_XEN_IBT /* Announce the function to ENDBR clobbering logic. */
+static const typeof(ctxt_switch_masking) __initconst_cf_clobber __used csm =
+    intel_ctxt_switch_masking;
+#endif
+
 /*
  * opt_cpuid_mask_ecx/edx: cpuid.1[ecx, edx] feature mask.
  * For example, E8400[Intel Core 2 Duo Processor series] ecx = 0x0008E3FD,
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.18